Deformable casing joining cable ends

ABSTRACT

Casing for protecting joined cable ends surrounded by variable volume insulation which is of maximum cross-section at its center and tapers to a smaller size at its ends and which has longitudinally extending corrugations to permit it to expand and contract and thereby follow the volume variations of the insulation.

United States Patent Appiani et a]. [451 July 18, 1972 [s41 DEFORMABLECASING JOINING 174/76, 88 R, 21 R CABLE ENDS [56] References Cited [72]Inventors: Edoardo Appiani, Milan; Alberto Felici,

Monza, both of Italy FOREIGN PATENTS OR APPLICATIONS [73] Assignee:Pirelli Societa- Per Azioni Centro Plrelli, 397,539 8/ I933 GreatBritain ..l74/l3 Milan, Italy Filed: O 1970 Primary ExammerDarrell L.Clay Appl. No.: 85,469

Foreign Application Priority Data FieldofSearch l74/l3, 12 R, 89,91-93,

Attorney-Brooks, Haidt & Haffner 57] ABSTRACT Casing for protectingjoined cable ends surrounded by variable volume insulation which is ofmaximum cross-section at its center and tapers to a smaller size at itsends and which has longitudinally extending corrugations to permit it toexpand and contract and thereby follow the volume variations of theinsulation.

10 Claims, 3 Drawing Figures Patented July 18, 1972 INVENTOES fl-7% HTTOwas DEFORMABLE CASING JOINING CABLE ENIB The present invention concernsan improved casing for restoring the-continuity of the sheath of a poweror control cable and is installed over an insulated cable jointprotected with insulating compositions which vary their volume, inconsequence of thermal or chemical-physicalactions, from the moment ofthe joint installation to its coming into service. The casing, byvarying its shape, follows the volume variations of said insulatingcompositions.

It is known that, when joints are made in sheathed cables, the cableinsulation is locally destroyed and the electrical or mechanicalcontinuity of the sheath is interrupted. Both must therefore be restored.before the cable is put into operation. Therebuilding of the sheath iscarried out by disposing around the joint, in such a way as to cover itscentral portion, a sleeveshaped casing, having tapered ends, the endopenings of which have a size slightly greater than the outer diameterof the cable sheath to which they are welded or joined.

The cable insulation, appropriately rebuilt over the joint, is protectedwith an insulating composition supplied to the interior of the casingthrough a suitable pouring inlet.-

Insulating compositions of various kinds, in particular, hotpouring orcold-pouring compositions, are used for this purpose.

Hot-pouring compositions, which at room temperature are in a solid orhighly viscous state, must be fluidized by heating in order to permitpouring thereof and to cause it to penetrate into all recesses of thecasing, as well as to permit an easy filling of the latter. After itspouring, the compositions cools and consequently shrinks. The cooling,for the most widely used compositions, is carried out for a time periodvariable as a function of the involved volumes and of the physicalcharacteristics of the material and in any case, it lasts several hours.During the cooling time, the interior of the casing must remainaccessible for refilling purposes, which is intended to eliminate mainlythe space left free within the casing after shrinkage of the compositionin order to avoid, inside the joint when in service, the presence ofundesired air bubbles or hollow spaces, which would impair theperformance of the joint and hence, the cable.

If cold-pouring insulating compositions are used for filling the casing,these undergo an exothermic reaction, so that initially they beat up andexpand, and after the reaction, the poured composition cools andconsequently shrinks.

, In order to prevent said volume variations from producting air bubblesor hollow spaces inside the joint, it is necessary to carry out, evenwith the cold pouring compositions, a final preparation phase, postponedfor several hours, during which the joint must remain accessible.

The need of maintaining the joint accessible in the interval of somehours between the initial preparation of the joint and its being placedin service is technically disadvantageous. Such need prolongs the totaltime necessary for the joint installation and consequently delays theplacing of the cable into service. If the cable is laid underground,which is the most frequent situation, the trench must be left open for along time, depriving large built-up areas of primary utilities orexcluding traffic from important highways.

The present invention aims at providing'an improved casing for power andcontrol cables having conductive or insulating sheaths, which obviatesthe above indicated disadvantages and does not require refillingoperations, or other operations required by the need of eliminating airbubbles or hollow spaces inside the joint in the time interval betweenthe initial installation and the coming into service of joints preparedwith insulating compositions subject to volume variations due to thermalor chemical-physical actions.

More precisely, the object of the present invention is an improvedcasing for restoring the continuity of the covering sheath of a power orcontrol cable over a joint protected with insulating compositionssubject to volume variations from the moment of the joint installationto its coming into service,

characterized in that the body of said casing is at least partiallyprovided with longitudinal corrugations able to facilitate and to orientits deformation and its consequent variation of capacity, the medianlongitudinal section of said body having a main central portion ofmaximum transverse size and two lateral portions tapered to a sizeslightly greater than the size of the sheaths of the two joined cablelengths.

The enclosed sheet of drawing illustrates by way of example a preferred,practical embodiment of the invention, in which drawing: I

FIG. 1 is a side elevation view of a preferred embodiment of the casingaccording to the invention assembled on the joint of a cable having ametallic covering sheath; I

FIG. 2 is the cross-sectional view taken along the line A--A indicatedin FIG. 1 before the insulating composition of the hot-pouring type ispoured into it; and

FIG. 3 represents the same cross-section shown in FIG. 2, after thepouring and the shrinkage of the hot-pouring insulating composition.

As shown in FIG. 1, the two cable lengths l0 and 10" are connected bymeans of a joint enclosed within the casing 14, whose body is preferablymade of lead or of another conductive material, and is secured to themetal sheaths of the cable lengths l0 and 10" by welds 12, 12" at thecasing end openings l3, 13'', respectively.

The casing 14 is constituted by two half-shellsl4' and 14",respectively, a lower one and anupper one. The lower halfshell 14 isprovided on its longitudinal edges with two L- shaped seats 15' and 15"(see FIGS. 2 and 3), the inner por tions of which receive, during theassembling, the corresponding edges 16, 16" of the upper half-shell 14".

A pouring inlet 17, provided with a lid 18, is provided in the centralportion of the half-shell 14". The two half-shells 14' and 14" aresecured together by welds l9 and 19', such as, lead or solder, effectedalong the longitudinal contact zones between the seats 15' and 15" andthe edges 16' and 16'.

The body of the casing 14 can be divided longitudinally into threepositions, namely: a main central portion 20 of substan tiallyrectangular shape, as viewed from the side, and two oppositely taperedlateral portions 21' and 21" of trapezoidal shape, the smaller bases ofwhich are slightly greater than the diameter of the metallic sheathscovering the two cable lengths to be joined.

In the preferred embodiment illustrated in the figures, the main centralportion 20 can be inscribed in a cylinder, and the two lateral portions21' and 21" can be inscribed in truncated cones tapered towards theircorresponding entry openings 13 and 13".

The body of the casing 14 is provided with longitudinal corrugations 22which extend along the whole main central portion 20 and are prolongedat 22 and 22" in the lateral por-v tions 21 and 21" along thegeneratrices of the corresponding circurmcribed frustum of cone, butinterrupted at a predetermined distance from the two openings 13 and13".

After the casing is assembled on the joint, an insulating composition,solid at room temperature, is poured into the casing 14 for instance, athigh temperature, until the composition overflows the opening 17. Then,the casing is tightly closed with the lid 18, sealed at 23, and at thistime, normal conditions can be reestablished inside the joint betweenthe two cable lengths l0 and 10" by carrying out further operationsoutside the joint, such as by closing the trench immediately afterwards.In the meantime the composition cools, with corresponding shrinkage, andcreates a depression inside the tightly closed casing. The outeratmospheric pressure acting on the casing 14, whose deformability isfacilitated and oriented by the longitudinal corrugations, compels thecasing itself to adhere to the composition and to follow the volumevariations of the latter, passing therefore from the configuration 24 tothe service configuration 24' (see FIG. 3).

Even if cold-pouring compositions are used, the composition is poured,as described above, until the composition overflows the casing withrespect to the pouring inlet 17; then, the lid 18 is closed and tightlysealed at 23. The exothermic reaction which takes place in theinsulating composition causes an initial expansion which, acting on thecorrugated walls, increases the capacity of the casing and equalizes itto the volume of the therein contained insulating composition. When thereaction is over, the insulating composition begins to cool and toshrink, and this variation is followed by the casing wall subjected tothe outer atmospheric pressure.

It will be understood by those skilled in the art that the details ofconstruction of the present invention can be varied as necessary. Forexample, the conductive or insulating casing could be built up with adifferent number of sections or with differently located joints betweensections and the longitudinal corrugations could be discontinuous oralternate or could be formed of combinations of channels and projectionsdifferent from the regular, sinusoidal corrugations illustrated by wayof example. Also the cross-section of the theoretical area in which theportions of the casing are circumscribed could be other than circular.Another form is, for example, an ellipse or a polygon.

What is claimed is:

1. An electric cable joint between a pair of cable sections, said cablesections each having a conductor surrounded by a sheath and said jointcomprising an interconnection between the conductors of said sections, acasing enclosing said interconnection and extending longitudinally ofsaid joint from the sheath of one cable section to the sheath of theother cable section, said casing being substantially unbroken in thelongitudinal direction and comprising a hollow central portion ofmaximum cross-section greater than that of the sheaths of said sectionsand that of said interconnection, and at opposite ends thereof, having apair of hollow, tapered, end portions forming a continuation thereof,each end portion having an end opening smaller than the cross-section ofsaid central portion and each surrounding and joined to one of thesheaths of a cable section, and void-free solid insulation within saidcasing and surrounding said interconnected cable sections, said casingbeing in complete contact with said insulation with no void spacestherebetween, said casing being provided with a plurality oflongitudinally extending corrugations disposed peripherally of at leastsaid central portion thereby pemiitting said casing to expand andcontract in volume and outwardly with respect to said conductors.

2. A joint as set forth in claim 1 wherein said casing is made ofconductive material.

3. A joint as set forth in claim 1 wherein the central portion of thejoint has a generally circular cross-section and where the end portionshave the shape of truncated cones.

4. A joint as set forth in claim 3 wherein said corrugations extend thefull length of said central portion and along at least part of thelengths of said end portions.

5. A joint as set forth in claim 4 wherein said corrugations terminateat points spaced from the end openings.

6. A joint as set forth in claim 5 wherein said casing is made ofconductive material.

7. A joint as set forth in claim 5 wherein at least the major portion ofthe periphery of the casing is corrugated.

8. A joint as set forth in claim 1 which comprises a plurality of partswhich interconnect along longitudinally extending seams.

9. A joint as set forth in claim 8 which comprises a further opening inone of said portions and a cover for said further opening.

10. A cable joint as set forth in claim 1 wherein said sheaths and saidcasing are made of metal and said sheaths are secured to the ends ofsaid casing with an electrically conductive connection therebetween.

1. An electric cable joint between a pair of cable sections, said cablesections each having a conductor surrounded by a sheath and said jointcomprising an interconnection between the conductors of said sections, acasing enclosing said interconnection and extending longitudinally ofsaid joint from the sheath of one cable section to the sheath of theother cable section, said casing being substantially unbroken in thelongitudinal direction and comprising a hollow central portion ofmaximum cross-section greater than that of the sheaths of said sectionsand that of said interconnection, and at opposite ends thereof, having apair of hollow, tapered, end portions forming a continuation thereof,each end portion having an end opening smaller than the cross-section ofsaid central portion and each surrounding and joined to one of thesheaths of a cable section, and void-free solid insulation within saidcasing and surrounding said interconnected cable sections, said casingbeing in complete contact with said insulation with no void spacestherebetween, said casing being provided with a plurality oflongitudinally extending corrugations disposed peripherally of at leastsaid central portion thereby permitting said casing to expand andcontract in volume and outwardly with respect to said conductors.
 2. Ajoint as set forth in claim 1 wherein said casing is made of conductivematerial.
 3. A joint as set forth in claim 1 wherein the central portionof the joint has a genErally circular cross-section and where the endportions have the shape of truncated cones.
 4. A joint as set forth inclaim 3 wherein said corrugations extend the full length of said centralportion and along at least part of the lengths of said end portions. 5.A joint as set forth in claim 4 wherein said corrugations terminate atpoints spaced from the end openings.
 6. A joint as set forth in claim 5wherein said casing is made of conductive material.
 7. A joint as setforth in claim 5 wherein at least the major portion of the periphery ofthe casing is corrugated.
 8. A joint as set forth in claim 1 whichcomprises a plurality of parts which interconnect along longitudinallyextending seams.
 9. A joint as set forth in claim 8 which comprises afurther opening in one of said portions and a cover for said furtheropening.
 10. A cable joint as set forth in claim 1 wherein said sheathsand said casing are made of metal and said sheaths are secured to theends of said casing with an electrically conductive connectiontherebetween.